* Yen's resilience due to short-covering, not just safe-haven play-traders
* IMM data shows dollar-long bets pared for 5th straight week
* China yuan weakens after trading band widened over weekend
By Lisa Twaronite
TOKYO, March 17 (Reuters) - The yen lost some ground against the dollar and euro but remained near the tops of its recent ranges on Monday as Western countries warned of sanctions on Russia after Crimea voted to separate from Ukraine.
Over 90 percent of Crimean voters chose in a referendum to join Russia on Sunday, an outcome that was denounced by leaders in Western powers and Kiev as a sham.
U.S. President Barack Obama said Washington rejected the results of the referendum and warned that the United States stood ready to impose sanctions on Moscow.
The dollar and euro hit their respective session highs shortly after Tokyo's 0100 GMT fixing, with Japanese importers said to be among buyers, market participants said.
Some also attributed the yen's resilience to short-covering rather than traditional safe-haven plays.
"Investment managers continue to hold a very short-yen position, so I think there could possibly be some position adjustments going on," said Bart Wakabayashi, head of forex at State Street in Tokyo.
"Obviously, when there's risk, there's an element of safe-haven flow, but I think there are adjustments going on as well," he said.
The latest data from the Commodity Futures Trading Commission released on Friday showed that speculators pared bullish bets on the U.S. dollar for a fifth straight week through March 11, with net longs falling to their lowest in more than four months.
Overall, though, investors have maintained net long positions on the dollar for 19 consecutive weeks. The last time speculators were short the greenback was in late October 2013.
A record drop in foreign governments' holdings of U.S. Treasuries led some to speculate that Russia has been reducing its dollar reserves ahead of possible sanctions from the West.
The dollar was last up about 0.2 percent on the day at 101.52 yen, near its session high of 101.57 yen but still a far cry from a 1-1/2-month high of 103.77 yen hit as recently as March 7.
The euro was up about 0.1 percent at 141.16 yen after rising as high as 141.27 yen, but remained well shy of its March 7 high of 143.79 yen, which was its highest since Jan. 2.
Against the greenback, the euro slipped slightly to $1.3901 . It remained not far from a 2-1/2-year high around $1.3967 touched on Thursday, before European Central Bank President Mario Draghi knocked it lower when he voiced concerns about its strength.
Asian investors were also considering the implications of Beijing's announcement on Saturday that it will double the daily trading range for its yuan. The step was viewed as a sign of confidence that the central bank had successfully fought off a plague of currency speculators.
The yuan weakened in opening deals on Monday.
"I don't see any major currency flows related to the yuan today, but people generally see it as a step in the right direction by Beijing," said a sales trader at a U.S. bank in Tokyo.